1. X472 HVAC System Design Considerations
Class 5 – System Selection 1 – Class
Exercises
Todd Gottshall, PE
Western Allied
Redwood City, CA
Reinhard Seidl, PE
Mark Hydeman, PE
Taylor Engineering
Alameda, CA
Fall 2015
2. 2
General
Contact Information
Reinhard: rseidl@taylor-engineering.com
Mark: mhydeman@continual.net
Todd: tgottshall@westernallied.com
Text
• None
Slides
• download from web before class
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3. 3
Course Outline
Date Class Topic Teacher
9/02/2015 1. Introduction / Systems Overview / walkthrough RS
9/09/2015 2. Generation Systems TG
9/16/2015 3. Distribution Systems RS
9/23/2015 4. Central Plants TG
9/30/2015 5. System Selection 1 - class exercises RS
10/07/2015 6. Specialty Building types (High rise, Lab, Hospital,
Data center)
TG
10/14/2015 7. System Selection 2 - class exercises RS
10/21/2015 8. Construction codes and Project delivery methods TG
10/28/2015 9. 2013 T24 and LEED v4 MH
11/04/2015 10. Life-Cycle Cost Analysis and exam hand-out TG
There are three instructors for this class. Todd Gottshall (TG), Reinhard Seidl (RS)
and Mark Hydeman (MH). The schedule below shows what topics will be covered by
who, and in what order.
4. 4
Class Outline
Today’s class consists of a workshop in class. You will split into groups and discuss (6) Case studies to determine what
system you would select for the buildings in question, and why. Please use the “system selection” worksheets to answer
what systems are appropriate and what systems are not appropriate, then hand these in after class.
The answers will be presented in class, and will be posted on the ftp site after class
Case Building Size, sqft Floors HVAC Budget
$/sqft incl. controls
Year
1 School 15,000 3+mezz. 50 2015
2 Office Building 500,000 2 40 2015
3 Airport Terminal 640,000 2 50 2010
4 Downtown College 150,000 17 25 2010
5 Fire Station 10,000 1 18 2005
6 Medical Office 100,000 5 40 2005
7 City Library 45,000 2 22 2005
8 Green Office / multi-use govt 20,000 2 35 2005
9 Sustainable school 20,000 1 20 2005
5. 5
Private School
Owner: Higher education private school
Building Size: 15,000 ft2
Uses: Classrooms and meeting areas
# Floors: 3 floors, mezzanine between floor 1 and 2
HVAC Budget: $50/ft2
Other Considerations:
No dedicated maintenance crew. Existing building
retrofit, wood frame building, very small existing shafts,
and mostly exposed ceilings.
6. 6
Office Building HQ
Owner: Private corporate tenant, HQ
Building Size: 500,000 ft2
Uses:
Office, Conference areas, Food service, Open atrium for
large events, IT labs for computer service
# Floors: 2 + mezzanine above garage
HVAC Budget: $40/ft2
Other Considerations:
High energy efficiency, “flagship” type building, LEED
platinum goal.
7. 7
Airport
Owner: Airport Terminal
Building Size: 650,000 ft2
Uses:
Check-in and departure lobbies, baggage claim,
restaurant and frequent flyer lounge areas
# Floors: 2
HVAC Budget: $50/ft2
Other Considerations:
Vary large, wide open areas, high traffic
Jets cause contamination of outside air intakes
8. 8
Downtown College Campus Program
Owner: Community College
Building Size: 150,000 ft2
Uses:
Classrooms, Offices, Library, Administrative Offices,
Science and Computer Labs, Conference Facilities
# Floors: 17
HVAC Budget: $25/ft2
Other Considerations:
Floor to floor height of 12’-6” to minimize project
height.
Energy efficient design requested.
9. 9
Fire Station Program
Owner: City Government
Building Size: 10,000 ft2
Uses:
Fire Station: truck parking, sleeping, dining, offices,
workout areas
# Floors: 1
HVAC Budget: $18/ft2
Other Considerations:
City maintenance personnel request easy access for
maintenance of equipment, would like to avoid going on
the roof.
10. 10
Medical Office Building Program
Owner: Non-Profit Medical Group
Building Size: 100,000 ft2
Uses: Office, Medical Exam Rooms, Waiting Areas
# Floors: 5
HVAC Budget: $40/ft2
Other Considerations:
High air change rates for exam rooms and
treatment rooms
11. 11
Library Program
Owner: City Government
Building Size: 45,000 ft2
Uses:
Library, offices, homework center, community meeting
rooms, café, computer room
# Floors: 2
HVAC Budget: $22/ft2
Other Considerations: LEED project
12. 12
Green Office Building Program
Owner: City Government
Building Size: 20,000 ft2
Uses:
City Hall, Police Department, City Services, Meeting
Space, Emergency Operations Center
# Floors: 2
HVAC Budget: $35/ft2
Other Considerations:
LEED project
Client wanting to “push the envelope”
13. 13
Sustainable School Building Program
Owner: Private Elementary School
Building Size: 20,000 ft2
Uses: Classrooms, Offices, Multi-Purpose Room
# Floors: 1
HVAC Budget: $20/ft2
Other Considerations: LEED Platinum project
14. 14
Private School
Owner: Higher education private school
Building Size: 15,000 ft2
Uses: Classrooms and meeting areas
# Floors: 3 floors, mezzanine between floor 1 and 2
HVAC Budget: $50/ft2
Other Considerations:
No dedicated maintenance crew. Existing building
retrofit, wood frame building, very small existing shafts,
and mostly exposed ceilings.
15. 15
Private School
VRV system selected – limited centralized
rooftop equipment for low maintenance
and low weight. Zoning flexible and allows
for sudden load changes.
VRV selected over split units because
somewhat more efficient (can take
advantage of some energy regain if winter
classroom is mostly empty and wants heat
while another is cooling because full)
Less refrigerant piping in VRV than splits
16. 16
Private School
Wide open areas
with high floor-to-
floor thanks to
mezzanine layout,
but no ceilings for
mechanical
equipment or
distribution
Very small shafts
(hard to run
economizer-sized
ducts in shaft or
space)
17. 17
Private School
Wide open areas
with high floor-to-
floor thanks to
mezzanine layout,
but no ceilings for
mechanical
equipment or
distribution
Very small shafts
(hard to run
economizer-sized
ducts in shaft or
space)
18. 18
Private School
Spaces with large
load changes
served with VRV
fan-coil units in
mezzanine /
corridor areas,
with just ducts in
main classroom
areas visible
Mezzanine
2nd Floor
20. 20
Office Building HQ
Owner: Private corporate tenant, HQ
Building Size: 500,000 ft2
Uses:
Office, Conference areas, Food service, Open atrium for
large events, IT labs for computer service
# Floors: 2 + mezzanine above garage
HVAC Budget: $40/ft2
Other Considerations:
High energy efficiency, “flagship” type building, LEED
platinum goal.
21. 21
Office HQ
Radiant floor system for open atrium areas
on ground floor – provides conditioning
for wide open areas and at the same time,
insulates ground floor from garage
underneath
UFAD for upper story open areas
VAV-RH system for conference rooms and
private offices
Fan-powered terminals for perimeter open
areas
24. 24
Office HQ
VAV for office
areas
VAVRH for
conference areas
(with HW reheat)
Fan-powered VAV
with HW reheat for
perimeter areas
25. 25
Office HQ
UFAD for second
floor open office
areas (perimeter
areas) and
VAVRH for
interior core
conference areas
26. 26
Airport Terminal
Owner: Airport Terminal
Building Size: 650,000 ft2
Uses:
Check-in and departure lobbies, baggage claim,
restaurant and frequent flyer lounge areas
# Floors: 2
HVAC Budget: $50/ft2
Other Considerations:
Vary large, wide open areas, high traffic
Jets cause contamination of outside air intakes
36. 36
Downtown College Campus Program
Owner: Community College
Building Size: 150,000 ft2
Uses:
Classrooms, Offices, Library, Administrative Offices,
Science and Computer Labs, Conference Facilities
# Floors: 17
HVAC Budget: $30/ft2
Other Considerations:
Floor to floor height of 12’-6” to minimize project
height.
Energy efficient design requested.
37. 37
Downtown College Campus
HVAC Selection
VAV-RH system selected – low initial cost,
centralized rooftop equipment keep
maintenance and noise out of classrooms
Water-Cooled CHW plant selected for
efficiency and compact size
38. 38
Downtown College Campus
VAV Reheat
with custom
AHU
Water-
Cooled CHW
plant
Natural Gas
Boiler HW
system
Large Custom AHU
Supply
And
Return
Shaft
Relief
Fans
Cooling
Towers
Boilers
Chillers
40. 40
Downtown College Campus
Typical Floor
First Design approach – all underfloor, with different
engineer (Designed SD, DD, CD) – too expensive (June
2006)
Second approach – (Designed SD, DD) – too high, too
much duct, shaft in wrong place, raises floor-to-floor
height
See http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/10/02/DDMRSFO5T.DTL
Third approach – re-started 2011, just went to re-bid as
14 story structure since former city college chancellor
was charged with with mis-use of university funds
See also http://cbs5.com/local/philip.day.CCSF.2.1085154.html
41. 41
Downtown College Campus
Final version Typ. Floor
VAV
Reheat
boxes at
each
classroom
Plenum
return
above a
tunnel
corridor
42. 42
Downtown College Campus
Roof
Note dual
fans for
main
supply
Arranged
to blow
into main
duct
top/bottom
for low
pressure,
fan scrolls
reversed
43. 43
Downtown College Campus
Roof
Note dual
fans for
main
supply
Arranged
to blow
into main
duct
top/bottom
for low
pressure,
fan scrolls
reversed
Front
Rear
44. 44
Fire Station Program
Owner: City Government
Building Size: 10,000 ft2
Uses:
Fire Station: truck parking, sleeping, dining, offices,
workout areas
# Floors: 1
HVAC Budget: $18/ft2
Other Considerations:
City maintenance personnel request easy access for
maintenance of equipment, would like to avoid going on
the roof.
45. 45
Fire Station HVAC Selection
Packaged Single-Zone Units converted to
VAV through VVT system approach
Small system with good control and low-
cost
47. 47
Fire Station Enlarged Floor Plan
Gas-Electric AC units
located at grade for
access, nothing on the
roof
VVT distribution
system
(inexpensive VAV with
a CAV unit)
AC Unit
bypass connects
supply to return
49. 49
Medical Office Building Program
Owner: Non-Profit Medical Group
Building Size: 35,000 ft2
Uses: Office, Medical Exam Rooms, Waiting Areas
# Floors: 5
HVAC Budget: $30/ft2
Other Considerations:
High air-change rates due to code requirements
for medical office buildings in exam rooms and
procedure rooms
50. 50
Medical Office Building HVAC Selection
DFDD System selected – high air change
rates mean lots of reheat, so DFDD is a
good fit since it does reheat efficiently
Packaged rooftop equipment selected as a
low-cost approach
53. 53
Library Program
Owner: City Government
Building Size: 45,000 ft2
Uses:
Library, offices, homework center, community meeting
rooms, café, computer room
# Floors: 2
HVAC Budget: $22/ft2
Other Considerations: LEED project
54. 54
Library HVAC Selection
Underfloor Air Distribution selected
because it can server large open areas
efficiently
Air-Cooled CHW plant selected for good
control of leaving air temperature needed
in UFAD projects
59. 59
Library Project Value Engineering
Project over budget (crazy bid climate)
Evaluated switching to electric reheat
• $110,000 savings
• $1,000 / year utility cost increase (municipal
electricity rate is low)
• 2% LEED energy savings penalty
60. 60
Green Office Building Program
Owner: City Government
Building Size: 20,000 ft2
Uses:
City Hall, Police Department, City Services, Meeting
Space, Emergency Operations Center
# Floors: 2
HVAC Budget: $35/ft2
Other Considerations:
LEED project
Client wanting to “push the envelope”
61. 61
Green Office Building HVAC Selection:
“Mixed Mode”
Why not a completely passive building?
• Too hot for natural ventilation only
• Simulation tools are crude so we have less
confidence in passive buildings
Mixed mode can be “best of both worlds”
• Passive, “open” building in mild weather
• Comfortable in hot weather
• More confidence in design
Cooling mode with IDEC System
65. 65
HVAC System Design
Dual Duct Variable Air Volume
• Reduces reheat and fan energy
100% Outside air during cooling
• Return air through space
• Conducive to natural ventilation
Mixed-Mode controls
• Indicator lights inform occupants
when to open windows
• Complicated controls
• Potentially large energy savings
Night cooling of thermal mass
67. 67
Sustainable School Building Program
Owner: Private Elementary School
Building Size: 20,000 ft2
Uses: Classrooms, Offices, Multi-Purpose Room
# Floors: 1
HVAC Budget: $20/ft2
Other Considerations: LEED Platinum project
68. 68
Sustainable School HVAC Selection
Natural ventilation through operable
windows throughout the building
Radiant heating chosen for quiet,
comfortable operation
No cooling, project is in a mild climate and
well shaded, with good glass and not too
much (integrated design)
71. 71
Operable Windows
All areas in
classroom less
than 20 feet
from an
operable
window or
skylight, so
rooms can be
naturally
ventilated
72. 72
Positive Fresh Air Fans for
Each Classroom
Small, quiet, fresh
air fans ducted
directly to outdoors
provided to
guarantee fresh air
even when windows
are closed
74. 74
System Selection Problem
Art as much as science
Compare:
• First Cost
• Energy Cost
• Maintenance Requirements and Cost
• Coordination with other Trades
• Spatial Requirements
• Acoustics
• Flexibility
• More …
75. 75
System Selection Approach: Matrix
Attributes and criteria listed and weighted
System Options listed and described
Each Option is ranked against other
options on each criteria – typically use a
“10 point must” system
Overall Score: ii rankweight
76. 76
System Selection Matrix: Rules
Weights must add up to 100
Criteria, Weights, and Ranks all adjusted
for each project
Serves as a vehicle for discussion among
system options
80. 80
System Selection Matrix:
Example Page 3 of 3
Note: the matrix was taken from the
advanced VAV design guide
• http://www.energy.ca.gov/2003publications/CEC-
500-2003-082/CEC-500-2003-082-A-11.PDF
